I try to maintain a reasonably bee-friendly property, out here in the wilds of Northern Virginia.
It’s not just that I need them to pollinate my vegetable garden. Or that bumblebees do, in fact, sleep in squash blossoms (aw!). Or that the hum of bees at work in my garden marked the never-to-be-repeated peak of mid-pandemic suburban quiet (Post #G11).
It’s more bee-as-coal-mine-canary. If I’m doing something in the yard or garden that’s likely to be killing off my bees, odds are I shouldn’t be doing that. It’s a quick way to rule out some environmentally stupid behavior.
In any case, I’ve had a couple of bee hotels (native bee nesting boxes) kicking around my yard for a few years now. Shown above. But those were never very successful. It took years to get the first bees to use them. And I might get a one or two tubes filled, per year. There are clear exit holes on some tubes, so some new bees were produced.
But not a big hit, over all.
This year, on a whim, I bought a different model of bee hotel, at my local Home Depot. The Home Depot mason bee box is already working vastly better than the previous model. It’s been up a few days and I already have more tubes filled than I got in the first few years of the other model. In short, my bees love this new bee hotel.
Now that I’m finally doing something right, I’d like to keep that going. In a radical and very un-guy-like step, I actually read the directions. And — surprise — I’ve been clueless as to how these things actually work.
But now that I know, I realize this new bee motel is a fundamentally terrible design. Not for what you can see — that part’s OK. And, as noted, it’s definitely attracting bees. The problem is that those bamboo tubes are permanently attached. As discussed below, that’s a no-no. You want nice clean new nesting tubes each year. And that means that, unless I tear it apart next year, this lovely little bee hotel is a single-use disposable item.
So this post is going to summarize everything I think I learned about mason bee nest boxes (“bee hotels”). And about the difficulty of making smooth-ended splinter-free replacement tubes for this, from bamboo I have on hand.
Three-minute tutorial: Bee hotel or roach motel?
Key point: For best results, you need two bee hotels (or equivalent) for every site at which you wish to maintain a bee hotel.
You ideally want the female bees to use clean, new nesting materials each year. The use of new (or carefully sanitized) nesting tubes each year minimizes the presence of diseases and parasites in the nest. If you don’t keep the premises clean, your bee hotel can end up as the bee equivalent of a roach motel. With poor enough conditions, the bees check in, but they never check out. Your bee hotel becomes a catch-and-kill trap.
The problem is that each spring, some bees are ready to check into your bee hotel before your existing guests have checked out. Some are ready to lay their eggs before others have emerged from their cocoons. The reason for this chaos is that these bees are quite short-lived. The emerge, mate, forage for food, lay their eggs, and die, all in the course of a few weeks in the spring.
The solution is to put last year’s bee hotel (or, at least, the nesting tubes) aside in an “emergence box”, to give the bees time to emerge from their cocoons. At the same time, you need fresh, new nesting tubes nearby, for the emerging bees to lay the next generation of eggs. An emergence box is just an opaque weather-protected box with a small opening. This allows the newly-emerged bees to exit, but prevents bees outside the box from seeing (and therefore attempting to re-use) the old nesting tubes.
No matter how you cut it, you would ideally have two sets of nesting tubes in rotation at each bee hotel site. One set of clean, new tubes, for this year’s eggs. And last year’s tubes, from which bees continue to emerge. You want to keep the emergence box with last year’s nesting tubes near your new bee hotel, because, as noted above, the bees get right down to business as soon as they emerge.
Here are my five Ws for bee hotels.
Who? These bee hotels provide nesting places for some species of solitary bees, that is, bees that don’t form big communal hives. Mainly, that means these are NOT for honeybees. The bees that use these devices are typically referred to as “native bees”, but that’s imprecise. For one thing, bumblebees are typically native bees, but those are ground-nesting bees, and won’t use these tube-type bee hotels. Your primary target bee is a “mason bee”, so called exactly because they build those little mud walls at the end of the nesting tube where they’ve laid their eggs.
What? A bee hotel provides tubular structures into which a mason (or similar) bee lays eggs. The bee lays a series of eggs in the tube, providing each with food, separating them with mud walls, and capping off the tube with more mud. Over the course of a year (in some cases, two years), each egg hatches into a larvum (worm), eats the food that its mother left for it, pupates (cocoons itself), and eventually emerges from that cocoon, the subsequent year, as a bee.
When? The eggs are laid in spring. The eggs hatch/larvae emerge in summer. They cocoon in the fall. And they re-emerge as bees the next spring/summer. (In some areas, there are species that spend two years in the cocoon, but I’m not sure how relevant that is to most places.)
Place your bee hotel outside in the spring. It appears to be fairly important not to disturb this during summer, as the larvae are delicate. That means you attach it to something solid in the spring, so it doesn’t shake around, and you leave it alone. The larvae pupate in fall. At that point — late fall, early winter — they are tough enough to be moved. Place the bee hotel in a sheltered, unheated location (such as an unheated shed). Then, next spring, place the bee hotel (or the tubes from it) in an “emergence box”, move them back outside, and let the bees emerge as the weather warms. Google “emergence box”, but it’s basically a sheltered box with a hole in it, to let the hatched bees escape.
Some experts “harvest” the cocoons as an extra sanitation measure. They break open the nesting tubes, remove and possibly clean the cocoons exteriors, and place the cocoons in fresh material for eventual hatch-out in the spring. The claimed advantage of this is that it separates the bees from various parasites that may linger in the nesting tubes and this allows them to emerge from overwintering parasite-free. If you are going to do that, you need to use relatively fragile nesting tubes (paper liners, reeds) that allow the cocoons to be removed undamaged, and not sturdy ones such as bamboo tubes shown above.
As of this writing, it’s not clear to me how much of an advantage you gain by harvesting cocoons, or what evidence basis there is for it. The only obvious advantage is that if certain fungal diseases are present in the nest, you’ll see them if you harvest the cocoon. As I plan to use all-new materials each year, I’m not sure that’s much of a concern to me.
Where? These bee nests ought to be protected from rain, protected from getting cooked in the afternoon sun, and so on. he most common advice is to locate them to catch morning (but not afternoon) sunlight. They need to be firmly attached to something substantial because the larvae are delicate and don’t want to be tossed about. In plain sight, so the bees can find it. And near a ready source of mud. Because bees need mud to cap off their egg cells.
Upshot: Facing east-ish, under eaves if possible, firmly attached to something, near water or mud, maybe 5′ off the ground, and plainly visible.
Why and how? Different bee species want different sized tubes. So from the get-go, a rack of identical tubes limits the species that can use that particular hotel. The tubes need to be closed off at the back, in some fashion. The tubes need to be sturdy enough to keep out various bee predators. Paper straws alone, for example, appear to be frowned upon, thought to be too fragile to keep out certain types of bee predators. In rare cases, you need to put hardware cloth across the front to keep birds from pecking out the larvae. That’s only necessary if you wake up one morning and all the previously-filled tubes appear empty.
The simple upshot of all this is:
- Each Spring, put last year’s nest out in an emergence box.
- Nearby, place a clean, new nest out to attract bees.
- Each Fall, refurbish last year’s nest, to be placed out the next spring.
